Various metals, particularly noble metals such as platinum and nickel, are known to be useful as hydrogenation catalysts in various catalytic hydrogenation reactions carried out in the gaseous phase. For example, such hydrogenation catalysts are extensively used in the hydrogenation of a variety of unsaturated hydrocarbon gases, such as ethylene to form their saturated counterparts, such as ethane. A number of intermetallic alloy hydrogenation catalysts have been developed for this purpose in order to provide a catalytic material that has sufficient hydrogenation activity by virtue of a surface layer of the active noble metal, or other catalytic metal, yet is much more inexpensive to manufacture and replace after deactivation because of its alloy association with another, less expensive metal. Many nickel intermetallic alloys and platinum intermetallic alloys are well known hydrogenation catalysts, particularly the zirconium/nickel intermetallic alloys and the zirconium/platinum intermetallic alloys, as evidenced by the following prior art patents: Hawley U.S. Pat. No. 2,564,331; Taylor U.S. Pat. No. 3,235,515; Porta et al U.S. Pat. No. 3,746,658 and Dalla Betta et al U.S. Pat. No. 4,002,658.
Some of the most important properties necessary for hydrogenation and oxidation catalysts to be successful on a commercial basis are the hydrogenation or oxidation activity, the ability of the catalyst to resist gas impurity poisoning, particularly sulfur poisoning, and the ability of the hydrogenation or oxidation catalyst to be regenerated for further use after the catalyst has been deactivated by reaction with some impurity in the reaction gas stream, particularly the ability to regenerate after sulfur poisoning.
In accordance with the present invention treatment of an intermetallic alloy hydrogenation or oxidation catalyst by alternate oxidation and reduction steps, in either order, in at least a two-step process, preferably at least a three-step process, substantially and unexpectedly increases the ability of the hydrogenation or oxidation catalyst to resist deactivation by reaction with gaseous impurities, particularly hydrogen sulfide; increases the hydrogenation or oxidation activity of the catalyst; and unexpectedly enables the deactivated catalyst to be regenerated.